1. Field of the Invention
The present invention relates to a pixel structure and a liquid crystal display (LCD) panel having the pixel structure. More particularly, the present invention relates to an LCD panel with low color shift and a pixel structure thereof.
2. Description of Related Art
Thin film transistor liquid crystal display (TFT-LCD) has become the mainstream in display market for it having such advantages as high image quality, high space efficiency, low power consumption, and no radiation etc. Presently, the performance of an LCD is proceeding towards high contrast ratio, rapid response, and wide viewing angle, wherein a multi-domain vertically alignment (MVA) TFT-LCD and a multi-domain horizontal alignment (MHA) TFT-LCD are usually adopted to achieve wide-angle display.
FIG. 1 is a cross-sectional view of a conventional MVA TFT-LCD. Referring to FIG. 1, the MVA TFT-LCD 100 includes a TFT array substrate 110, a color filter substrate 120, and a liquid crystal layer 130. In particular, a protrusion 140 or a slit pattern (not shown) is disposed on the TFT array substrate 110 and the color filter substrate 120, so that the liquid crystal molecules 132 in the liquid crystal layer 130 orient in different directions to form a 4-domain distribution when an electric field is generated between the two substrates 120 and 130. Accordingly, a wide-angle display effect is achieved.
However, the MVA or MHA TFT-LCD still has the problem in color shift. Here, color shift refers to the phenomenon that when a user looks at a display from different angles, the user will see an image of different color tones. In particular, the image will produce a color washout effect when the user looks at the image from a large viewing angle. Color shift is produced because of the large luminance at medium or low gray scale, and the luminance at medium or low gray scale has to be reduced in order to reduce color shift. Thus, the U.S. Publication No. US2005/0030439 disclosed a pixel structure, wherein a pixel is further divided to form multiple domains.
FIG. 2 is a top view of a color filter substrate in U.S. Publication No. US2005/0030439, and FIG. 3 is a top view of a TFT array substrate in U.S. Publication No. US2005/0030439. Referring to both FIG. 2 and FIG. 3, a first pixel electrode 190a and a second pixel electrode 190b are respectively located in a left domain and a right domain of a pixel. The first pixel electrode 190a is electrically connected to a drain electrode 175 through a contact hole 181, and the drain electrode 175 is extended below the second pixel electrode 190b. Thus, a voltage over the second pixel electrode 190b drops due to capacitor's coupling effect, so that the voltage supplied to the second pixel electrode 190b is smaller than the voltage supplied to the first pixel electrode 190a. Because the voltage over the first pixel electrode 190a and the voltage over the second pixel electrode 190b are different, such a effect that the domain of the second pixel electrode 190b is darker at medium or low gray scale and the domains of the first pixel electrode 190a and the second pixel electrode 190b have close luminance at high gray scale can be achieved.
In addition, the drain electrode 175 is opaque, therefore the drain electrode 175 has to be disposed corresponding to the protrusion 272 on the color filter substrate in FIG. 2 so as to prevent the aperture ratio of the pixel from being reduced.
However, considering with different panel sizes and pixel resolutions, the distances between the protrusions or between slits have to be maintained in order to optimize the characteristics of the panel, such as response time, transmittance, and so on. Thus, in foregoing design, i.e., the left and right layout of the first pixel electrode 190a and the second pixel electrode 190b, it is difficult to adjust the area ratio of various pixel electrodes. And besides, if the panel shifts so that the drain electrode 175 is not disposed corresponding to the protrusion 272, the aperture ratio of the panel will be seriously affected.